This paper addresses the issue of whose genitalia are involved in the dissolution of the castration complex in boys. Freud and his followers suggested several different possibilities which are elaborated herein, and these alternative models are discussed from the perspective of psychological research regarding children's emergent gender identity and their awareness of genital differences. The reviewed data show that contrary to Freudian theory, preschool children's emergent gender identity is not dependent on their awareness of genital differences. However, preschoolers with younger siblings, primarily opposite gender ones, evidence greater understanding of genital differences, as Freud suggested. The discussion emphasizes the importance of children's family constellation and their awareness of self-other similarity and dissimilarity in the development of their gender identity.